LONDON (CNN) -- Olympic athletes and spectators are set for the biggest day of action yet at the London 2012 Games, with 25 gold medals up for grabs in 11 different sports on what has been dubbed "Super Saturday."
The world's fastest man, Jamaican sprinter Usain Bolt, gets his 100-meter campaign under way on day eight of the Games, in front of what is expected to be a packed stadium.
The home crowd will be cheering on Jessica Ennis, seeking gold in the heptathlon after a strong start Friday. She has long jump and javelin Saturday morning, with the 800-meter run as the final event.
Later Saturday, U.S. swimming legend Michael Phelps will swim in his last race, as part of the U.S. men's 4x100-meter medley relay team. He promised to retire after this competition.
On Friday, he clinched the 100-meter butterfly to capture his third gold medal of the London Games and the 17th gold of his career.
Phelps wasn't the only American to make history in the pool Friday. Missy Franklin, 17, from Pasadena, California, earned her third gold medal, and fourth medal overall, in the women's 200-meter backstroke, smashing the world record in the process.
Another American teenager, 15-year-old Katie Ledecky, also earned gold in impressive fashion, besting her nearest competitor by more than four seconds in the women's 800-meter freestyle.
The women's triathlon started Saturday morning with the swim in the chilly waters of the Serpentine, a lake in the middle of Hyde Park more usually home to swans, followed by the cycle and run elements on the roads around the park. Great Britain's Helen Jenkins went into the race one of the favorites; Team USA's Laura Bennett and Sarah Groff are also contenders.
In leafy west London, American tennis star Serena Williams faces Russia's Maria Sharapova in the women's singles final at Wimbledon.
Four rowing golds are at stake on the lake at Eton Dorney, outside London, with finals in the men's four, the men's and women's lightweight double sculls and the women's single sculls.
The United States' excellence at the Aquatics Centre helped them pass China for the most gold medals on Friday, with 21, on the seventh full day of the Games. Americans have 43 medals total, compared with 42 for the Chinese.
Great Britain also rocketed up the medal count chart, thanks to one of its athletes' best days yet. The host nation captured three gold medals, bringing its total for the Games to eight, just behind South Korea for the fourth most of any country.
But with 25 golds to be claimed Saturday, expect plenty of ups and downs in the medal table.
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